Imaging p53 in pancreatic ductal adenocarcinoma

Thesis

Pancreatic ductal adenocarcinoma (PDAC) represents 90% of pancreatic cancer cases and is characterised by poor survival rates and resistance to current therapeutic regimes as the majority of patients present with an already advanced disease at the time of diagnosis. Mutations of the TP53 tumour suppressor gene are a frequent event in tumourigenesis and appear in around 75% of pancreatic cancer cases just before the full development of PDAC and metastasis into the surrounding tissues. Molecular imaging tools, such as SPECT, using monoclonal antibodies specific towards tumour associated antigens, could aid the in vivo characterisation of biological processes and provide a non-invasive method for early diagnosis of cancer.

Toward this end, a commercially available mouse monoclonal antibody against total p53 protein (anti-p53 (1C12)) was selected. Anti-p53 (1C12) was first evaluated in vitro regarding its specificity and affinity in cell lines with variable p53 status, derived from a genetically engineered mouse model of PDAC (KPC mice). The subcellular localisation of the p53 protein in the cell lines used was also studied.

Following the selection of the antibody, the anti-p53 (1C12) was conjugated to the cell penetrating peptide TAT to facilitate cellular and nuclear translocation and then to p-SCN-Bn-DTPA to allow labeling with ¹¹¹In. Further in vitro evaluation was performed on the conjugated antibody, conferring subcellular translocation in fixed cells, unaffected binding affinity, favourable radiochemical yield and purity, and stability of the radioconjugate in serum. Retention of the radioconjugates was also observed and was signicantly different when compared to radiolabeled non-specific IgG₁-TAT in cells harbouring mutant p53.

The ability of ¹¹¹In-BnDTPA-p53 (1C12)-TAT to selectively target endogenously expressed p53 was assessed in vivo using mouse allograft tumour models of the cell lines evaluated in vitro, and in genetically engineered KPC mice. This provided a preliminary ''proof-of-principle" concept for diagnostic detection of PDAC. The knowledge acquired from the current study may be used to develop a first imaging tracer against p53 which could significantly improve the biological evaluation of cancer.

Authors: Koustoulidou, S

• DOI: 10.5287/ora-no6nde5oe
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford